Having recently finished "Brideshead Revisited" I starting thinking about this question. Waugh was a convert, but Brideshead was first and foremost a theological novel. The novel is in many ways about the "twitch upon the thread" by which God recalls sinners to himself. Other great novelists also had their Catholicism reflected in their writings -- Chesterton, Greene, Flannery O'Connor. Even Betty Smith's novel "A Tree Grows in Brooklyn" is very conscious of the Catholicism of its author.
Are their any Catholic writers today that fill this gap? I am told that the work of Mary Higgins Clark is informed by her faith, but I have never read her (I am not into thrillers). Obviously, there are novelists who are Catholic. But are there any Catholic novelists today?